Refactor transit_api into a repo/routes module split

Split the 5,441-line index.js into an 86-line bootstrap, thin domain
route modules, shared lib/ helpers, and a repo/ layer that isolates the
DEV_MOCK branches (repo/*.mock.js). Repo methods return {statusCode, body};
routes are one-line wrappers. Pin search_path to "transit.bus" and
document the /bus/ prefix with legacy root aliases (Deprecation header).

Parity verified: 57/57 byte-identical on the stub differential harness
plus 24/24 live read-only responses vs the original against real
PostgreSQL. The only intentional behavior change: mock reorder/delete
bus-line endpoints no longer require a live DB (previously 500 in
DEV_MOCK=1 without PG). DEV_MOCK gate and node --check clean.

transit_api/lib/report-error.js

@@ -0,0 +1,29 @@
+const { ERROR_LOG_API_URL } = require("./env");
+
+
+async function reportError({ partofservice, error }) {
+  try {
+    await fetch(ERROR_LOG_API_URL, {
+      method: "POST",
+      headers: {
+        "Content-Type": "application/json",
+        "x-internal-api-key": process.env.INTERNAL_API_KEY || "",
+      },
+      body: JSON.stringify({
+        service: "transit_api",
+        partofservice,
+        error,
+      }),
+    });
+  } catch (_) {}
+}
+
+
+function reportUnhandled(context, err) {
+  const message = err?.message || String(err);
+  const stack = err?.stack || message;
+  log("error", context, { error: message, stack });
+  void reportError({ partofservice: context, error: stack });
+}
+
+module.exports = { reportError, reportUnhandled };